Magnetic recorder



May 19, 1953 v H. A. HOWELL EI'AL 2,539,333

' MAGNETIC RECORDER Filed May 12, 1947 9 Sheets-Sheet 1' 5 3 2 Q H w r 3, a u w 9 .m n E F w a N Q EH A. 2 W0... 2 m 6 R 3 R o 3: rfl w w wk A 0 s W e .9 w i as o m um N a o x @v m #5 I .w Q g l M R MW w. m I 1 I l 0 11 u m M 0 p E R I n V m |M| l m f H. M II fi I1 m MU H I. x H W a .v Q Mk v o 7 II. 3 M HI h 5 l ail 9 2 1. l O w m NM m w M hwkulll. H M m y 1953 H. A. HOWELL ET AL 2,639,333

MAGNETIC RECORDER Filed May 12, 1947 9 Sheets-Sheet 5 Eli-Li- May 19, 1953 H. A. HOWELL ETAL 2,639,333

MAGNETIC RECORDER Filed May 12, 1947 9 Sheets-Sheet 4 iii-1 May 19, 1953 H. A. HOWELL El'AL 2,539,333

MAGNETIC RECORDER Filed May 12, 1947 Y 9 Sheets-Sheet 5 LIZ-.6.

223512 Zars f/uaw 14. MM?

, I finge B. Orr'urT H. A. HOWELL EI'AL 4 2,639,333

May 19, 1953 MAGNETIC RECORDER Filed May 12. 1947 9 Sheejs-Sheet 6 y 1953 H. A. HOWELL ETAL 2,639,333

MAGNETIC RECORDER Filed y 2. 1947 9 Sheets-Sheet 7 May 19, 1953 H. A. HOWELL ETAL 2,639,333

MAGNETIC RECORDER Filed May 12, 1947 9 Sheets-Sheet 8 IITFEJZYTFE b c/al/ 4. Hon Eu. [2/453 62 OFFUTT iL/y May 19, 1953 H. A. HOWELL ETAL 2,639,333

MAGNETIC RECORDER Filed May 12, 1947 9 Sheets-Sheet 9 men Dr's l/uw/ fl. lion/a1. fine-e A9. UFFurI tion to provide an improved recording and reproducing mechanism suitable for use with a lengthy magnetizable medium which may be operated to record, reproduce or rewind by manipulation of simple, foolproof, controls and without rethreading the medium.

The novel features which we believe to be characteristic of our invention are set forth with particularity in the appended claims. Our invention, itself, however, both as toits organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings.

On the drawings:

Figure 1 is an isometric view of the front anel and top portion of a magnetic recorder embodying the features of our invention.

Figure 2 is a top plan view of the recorder of Figure 1, but with the housing covering the head and associated elements removed.

Figure 2A is a diagrammatic view of the head showing the shape thereof and the positioning of the magnetizable tape relative thereto.

Figure 2B is a fragmentary cross sectional view through section IIB-IIB, Figure 2, and showing the switch and supporting elements associated with the listen-record operating arm.

Figure 3 is a view of the winding mechanism of the recorder of Figures 1 and 2 as seen when looking upward from a position directly below the support panel with the operating knob positioned in the stop position.

Figures 4 and 5 are cross section views taken along axes IVIV and VV, Figure 2, respectively, but not showing the head, erase magnet and elements associated therewith.

Figure 6 is a view like Figure 3, except that the drive motor and the supporting plate therefor are removed to show more clearly the operative elements hidden from view in Figure 3.

Figure '7 is another view like Figure 6, but with the flywheel and drivewheel removed to show clearly the portions of the mechanism hidden from view by these elements.

Figure 8 is a view like Figure '7, but showing the elements of the driving mechanism positioned for the rewind operation where the medium is caused to travel in direction opposite to the direction of travel during the recording or play-back operation.

Figure 9 is a view like Figures 7 and 8, but showing the elements of the drive mechanism positioned for the forward operation where the medium travels in direction for recording or play-back. 7

Figures 10 and 11 are fragmentary top views like Figure 2 but showing the position of the capstan and its associated elements when the medium travels in the rewind and the forward directions respectively.

Figure 12 is a schematic diagram of the electrical circuits employed in an embodiment of our 24, electrical operating knobs 248, 212, and 246, jacks 293 and 232, etc. A top panel 28 is provided to support the mechanical system, including the elements shown in Figures 1 and 2 supported above the panel and the elements shown in Figures 3 to 9 supported below the panel.

Above panel 28 are mounted medium supporting devices 30 and 32. A lengthy flexible recording medium 34 is coiled on these devices, so that upon rotation of devices 30 and 32 in like direction, medium 34 is passed between them. In traveling between devices 30 and 32, medium 34 passes within enclosure 36 where it travels across head 42, Figure 2, which converts the variations in magnetization along the length thereof to corresponding variations in a signal or, conversely, imparts variations in the magnetization of medium 34 along the length thereof in accord with the time variations of a signal.

The medium 34 may, for example, be a paper tape treated so as to be magnetizable. In one method of this treatment, a magnetizable coating is placed on the tape by drawing it through a suspension of magnetic particles so that particles are deposited on the tape and act as a magnetizable medium in connection therewith.

The operative elements which act upon medium 34 as it passes between devices 30 and 32 are shown most clearly in Figure 2 which is a top view of the mechanism of Figure l but with the enclosure 36 removed. From this view it will be apparent that the medium passes across guide pulley 38 and capstan 40 and in traveling between these elements passes across head 42 with linear velocity corresponding to the rotational velocity of capstan 40.

The construction of head 42 is shown in somewhat diagrammatic fashion in Figure 2A. As will be evident from this view, the head includes a core member 44 which, together with medium 34, defines a path for magnetic flux as is indicated by the dashed line 46. In addition, head 42 includes coil 48 having turns to link the flux of core 44 and medium 34. During recording operations, 2. time varying current is caused to flow in coil 48 by means to be described in further detail hereafter, so as to set up magnetic flux within head 42 and the incremental length of medium 34 positioned immediately over the air gap thereof. As capstan 40, together with devices 30 and 32 cause medium 34 to travel across head 42 at a uniform linear velocity, this causes variations in the magnetization of medium 34 to be imparted along the length thereof so as to magnetize medium 34 to a varying degree in accord with the time variations in the intelligence to be recorded. During the play-back operation, an amplifier is connected to coil 48 in a manner described in further detail hereafter, and medium 34 passed across head 42 by reason of the action of devices 30 and 32, together with capstan 40. As successive incremental lengths of medium 34 are positioned over head 42, different values of magnetic flux link coil 48. This causes a time varying electromotive' force to be induced in coil 48 in accord with the variations in the magnetization of medium 34 along the length thereof, thereby reproducing a time varying signal corresponding to the signal recorded on the medium.

The operative structure for transferring medium 34 between devices 30 and 32 is shown in the views of Figures 2 to 11. Figure 3 is a view of the mechanism as seen looking upward from below panel 28 and shows all the elements mounted thereon in connection with the mechanism.

as it passes thereover and hence removes undesired signals or noise previously imparted thereto. Moreover, member I28 has extending arm I34 which is located below panel 28 as may be seen in the view of Figure 9. Pin I38 is located at the remote end of this arm at a radius such as to be engaged by the projecting lip portion I38 of plate 88. I

When arm I26 is in the listen position shown in Figures 2 and 9, erase magnet I32 is swung to a spaced position relative to medium 34 so that no magnetization is imparted to the medium by magnet I32 and no erasure of the record takes place. In this condition, pin I36 is swung free from the projecting lip I38 of plate 88 and is not engaged thereby, even when plate 88 is swung to the position shown in Figure 8 where it has maximum movement in the clockwise direction as seen from that figure.

When arm I20 is swung to the record position as shown in the dotted lines of Figures 9 and 11, medium 34 rides on magnet I32 so that a uniform degree of magnetization is imparted thereto as it passes thereover. In this condition the switch I3I of Figure 2B is rotated so as to connect the electrical system so as to impart a time varying current to head 02 in accord with the time variations in an intelligence to be recorded. Moreover, pin I36 on arm I34 (Figure 9) is swung to a position where it engages the extending lip I38 of plate 88. Inasmuch as plate 88 is in the position shown in Figure 9 when medium 34 is being unwound from device 30, no interference between arm I34 and plate 88 takes place, and it is possible to record the intelligence desired.

One of the features of .our invention resides in the fact that the arm I28 is automatically returned to the listen position and magnet I32 spaced from medium 34 when the movement of medium 34 is stopped. This action takes place by reason of the engagement between pin I36 and lip I38. Thus if plate 33 is rotated in the counterclockwise direction as seen in Figure 9 so as to stop the unit, pin I38 is engaged by plate 88 so as to swing arm I26 to space erase magnet I32 relative to the medium 34 and prevent that magnet from affecting the medium.

Figure 2B is a fragmentary cross sectional view through the indicated cross section of Figure 2 and showing the method of supporting arm I26 relative to the top panel 28 and the front panel 22. As will be evident from this figure, arm I26 is supported on bushing I21 which is attached to shaft I30 so as to be supported thereby. Moreover, it will be evident that arm I28 extends below the surface of upper panel 28 as will be further evident from Figure 9. The shaft I30 is supported in switch I3I which is in turn supported from front panel 22 by bracket I29. The switch I3I is of conventional construction and includes at least six poles capable of moving in accord with the motion of armIZfi from the position shown in the solid lines of Figure 12 to the position shown in the dashed lines thereof.

Device 32 is supported from panel 28 by shaft I40, Figure 4. Pulley I42 is supported on shaft I40 and located below panel 28 so that rotation imparted to pulley I42 causes corresponding rotation of device 32. Pulley I42 is rotated in accord with the rotation of flywheel 16, Figure 5, by

reason of belt I44, Figure 6, which rides on that pulley and on pulley I46 which is attached to shaft 18.

Inasmuch as pulley I42, Figure 6, is driven through pulley I46, wheel 12, and shaft 68, pulley I42 rotates in the same direction as shaft 68. Moreover, it will be evident that the direction of motion imparted to shaft by section 84 of shaft 68 is opposite to the direction of rotation of shaft 68. Furthermore, flywheel 16 rotates in the same direction as shaft 68 by reason of the action of wheel 12. Thus, if shaft 88 is rotated in the clockwise direction as seen in Figure 6, shaft 80 is rotated in the counterclockwise direction when disk 82 is engaged by enlarged section 84 so as to tend to wind medium 34 upon device 30. Moreover, flywheel 16 and capstan 40 are rotated in the clockwise direction as seen in Figure 6 so that the velocity tended to be imparted to medium 34 by the action of capstan 40 is in direction to transfer medium 34 from device 30 to device 32. In addition, pulley I42 and device 32 are rotated in the clockwise direction as seen in Figure 6 when belt I44 is engaged so as to tend to wind medium 34 upon device 32. Thus, one direction of rotation of shaft 68 corresponds to winding action on both device 30 and device 32. This winding action is controlled by selectively engaging the drive in a manner to be described in further detail hereafter.

It is the function of plate I48, Figure 6, to tension pulley I44 in accord with the position of cam I50, Figure 6. Plate I48 is pivotally mounted about pin I52, and is disposed below the surface of panel 28. Spring I54, acting against pin I56 in panel 28 and pin I58 on plate I48, tends to retate plate I48 in the counterclockwise direction as seen in Figure 6, thereby swinging idler wheel I60 into engagement with belt I44 and tensioning that belt to achieve more effective driving action on pulley I42 by reason of the rotation of belt I44. Idler Wheel I50 is rotatably mounted about pin I62 to minimize the frictional drag on belt I44 associated with the presence of the idler mechanism.

Plate I48 is positioned in accord with the angular position of cam I50 by reason of the engagement of pin I64 with the peripheral surface thereof. Spring I54 acts to swing plate I48 so that pin I64 engages cam I50 and cam I50'is provided with a varying radius about shaft I66 so that the tension of belt I44 is altered in accord with the angular position of cam I50.

It is the function of plate I88 to act as a brake selectively to oppose rotation of device 32. To this end, plate I68 is pivotally supported from panel 28 by pin I10 and is provided with arm I12 having friction wiper I14 to engage edge I16 of pulley I42 to retard shaft I40. Spring I18, acting against pin I80 on panel 28 and pin I82 on plate I68, tends to swing plate I68 in the counterclockwise direction about pin I10 as seen in the view of Figure 6, thereby tending to cause engagemen of friction wiper I14. 1

It is the function of cam I84 to position plate I68 about pin I10 so as selectively to cause engagement of the friction wiper I14. To this end, pin I86 is located on plate I68 and is disposed so as to engage the peripheral surface of cam I84. Spring I18 biases plate I58 in a counterclockwise direction as seen in Figure 6 to cause engagement between pin I86 and cam I84. Thus as cam I84 is rotated and the radius between pin I86 and shaft IBBaltered, plate I68 is swung about pin I10 so as to cause engagement and disengagement of the wiper I14 to increase or decrease the braking torque on shaft I40.

It is the function of plate I88, Figure 7, to shift pinch wheel 204 and plate 88 in accord with therotation of cam I50. To this end, plate 9; iii is rivet-a l s p erteci p c s}. relationshis ith nanel 21% by sin iii and i hissed. in he ee n erslosk ise direet en a o t 1 1 it W i e-ins. .2 whi h sets, a ainst pin t P nel 28 a d-s n. We n. pl te ts, Bin ts lo ated to enga e ne erai surface, s s ne ii sq that sprin Hi2. causes n 1% t ngag m. i511 and thereby caus s p ate W o at about pm let in accord nce w h the rota io q cam mi! bo he axis of: shaft 15%- mterceu ee en be e pl e. ii and Plate 8i! s. provid d b flexibl co d. iii. which men. esaximle, be a e This rd s. a ta hes ts pla e is y pie H 3 a d is plate saw Pie 2%- adiustahie ass. is: prev ews t enable eiter= t o oihe en h of w re betwe n. p and pin Ziiiiso h t, t e n ereo wneetiiis re a tions ip be eenp s s an 8 a be ar ed: asm ch as ee ns- 9.4 s ries t swing pi te 8 in the, c unter ls wis ire t n. as s i F a= ure '4 ire iii is maintamed in a taut. condition and otat n-i: cam i s auses r ta i n o plate &8 about he c nt r of s sn iq it o. as to. shift dish & i o he p si ion wh r ra e fii is en aged Fi ure 9),. is a. posit n ere it i driven by enl e p r on 8A of shaf 5.3 ist ure 8).

In add ion o n conn ct ng p a 88; a d cam 50 pl te s; a ts. is pos ti n p ch whee 26 as erts wi h the d on of tra el o m dium .4 so that h p n W e e g g s me i m 3- i desi ed tra l n t e direc: tion eelpond n t h ci r i n o r ation o ca tan t, this. n nc Wheel 284 is rete eb v mou on shaf fies wh h extend hrough missi g 1 o panel 2 s w l he e i= dent irem. Figure Op nins 8%; s ha ed to permi m ment t shaft 2% and plate L8 in. awa d w t e m e en s o am 50- t, is, the; f unotion of the wipt as emb y Zli igure 2. to press me um again t sap/st in when medium as passes across capstan 40. in qppesitio is the retati n theme; In his. en a fri tion wise s sh a felt D d, 21%, is. msunte i sp ng summit 214 which is in turn rotetahly nene ted fireiii panel 8 by s n 2&5. The p o i e end. iii 0i sunii rt 4 1. is. hurries abou dle Wh l Z l iso that as isiler wheel is sw ms to e sp sedi rela ionship with mesium as the wiper assembly iii s rotates into nqsitio o p ss medium ii against Qanstan 41L In asserclemze with the ref red sm sd msnt i o r in eri ie i apstan M has a suries Qt pit material s ch L sa ll ys so hat as ium s drawn a ro e n taii 43 i an i mess-ed ther aga nst by i surie e aps an is i o s ed to uni orm radi s, sheet the of qte ioi a unii'erm movement of medium when v lesity is impart the et by s p-star; it th eby oidin ny ende sy toward Qnemtian Q eret i the mechan l ner s o our in en ion bes h inqers qssi b ref renss to the. v ews of Figu es 6 a d 9, a n

in ggnjungtion with the views 9 Figures 2, If) and 11. These views show the operating mechanism in the various operating positions.

In'the vies, of Figure '7, the unit is in the stop position Where the stop marking on dial 220 is aligned with the reference mar-k 2-22 of panel 28 as will be evidentfrom Figure 2. In this condition, the raaius arm of cam res which bears against pin I86 of plate M8 is of small value sothat the spring 118 swings plate 16$ against edge 1 i pulley M e sense. wip i ts eppose rotation of that disk and hence to. oppose reta iqn 0i device 2-- Eurthermera m4 of Plate ii-8, r des on, a P in o r l t v ly reat reams Qt 9 so hat h asins a t on 0i spring #5 is e srnem and id er he l its. does n t tens n be t 1% In he. s en po i ion o Figu e 1 the am! sectties is of plate ine is s en age th brake lit and sw ne, at br e fr e of wh el .82.. Thu d sk 32. s ree t rqtate when t e d al. 22 i shift d irqm the ew nd posi ion is the st p nos ti n and th e is no t ndsney -Q f e si vit iii to, be steere more sapidly than t m dium is is, r .i r windin hereon sh ul devise 9. he heior series. 3 when. the. dialv 2G is shifted from he re nd is th s n pos tion t e wou d be sn el d 0 ,1, as t e lett devic ould nreal the medium whe the r te tier; & the iormsr is inade uate. t take it Qsms i 11 and L are retaii ai in the stop nositien gainst the as iqn oi s rine H3 iii an i 54 hi not h &1 ii ii! n. Whitll. it rests This f rther indicates to the enerat r the th he ste nssitiq is reac,h$d-, The shrine iii a ting again t the not h 19,! causes tam ii. t leek the pos tion i knob 22K! is, rota ed to e iut vets ne r that pe i ion and then, rele ed; 7

s will. b evident ir iii Figure 2. the Risen Wheel 204 is swung to a Qisengaged; position reiwe. t 4G ii 2 i is r ated to the se s on results. ir iiit e fact tha the pin 1%, F gure id s en a iiqi it em 1511 having a resins restric s the retet' n Qi i te its y shu ii. to am unt o qeusesnsa 9i ixies wheel 2% with eansta 4, t e iric iqnai easement bet een medium i end. Q psiaii is. nly th iqt iiqnal ngagement as qq s esi with he o me ium ii hersqn Thi iris: ae ia engagement is inade uate to @euse motio at medium. 3. against the retarding ssti i iii. the brake 1 W iqh acts in o po e r ati n of d ise and; o arrest motien 0i. inscii m When he mechan m is in the st p os ion. Figures 2 and 7" t is impo sib e shi arm. iii i om the lisienf' izq i iqi hown in Fi u e. 2: to the rs-rd nqsi qri hown in h @Qt ines Qt Figur 1 Tiii is ue o t e fa t tha otati n i rm lit sens s serrss qnci ns r tation 9i arm i 14. riser L, Whiq rq etionsw nss in M t engage t e ext di 111 ms o at 83. This engagement prevents any} 128 from rota ng s ifiisi it t swing ase ma n cs2 n ens-seine p sit n w me i m 3 By the automatic action of plate 88 in preventing rotation of arm 12$ to the reeord -"position w avoid the possibility of accidentally e asi g: a res iins fh s e u s m t t that at the end of any recording operation it is necessary to stop the mechanisrn a movement that swings platefit to position of Figure '7 wherein arm 526 is swung to position magnet I32 to a spaced relationship relative to medium 34.

Figures 8 and 10 show the operating marina v nis n in the "rewind position where medium 34 is wound from device 32 to device 39. In this condition, dial 220 is swung to the position wherein the rewind marking is opposite the reference mark 222, Figure 2. As will be evident, from Figure 8, the pin 1% of plate i687 engages the extending portion 224 of cam H35, thereby preventing further rotation of dial 229 an gear 226. I'lais advises, the operator that the ewind position is reached and nrevfinfifi turnin iiai 11 220 beyond the "rewind position to the forward position.

In th rewind position, pin I86 rides on a portion of cam E84 having a relatively large radius so that the action of spring I18 is overcome and wiper I I4 swings free of wheel I42. Furthermore, pin I64 of plate I48 rides on cam I50 at a point of relatively large radius so that idler wheel I60 swings free of belt I44 to cause that belt to ride loosely on pulley I42. Thus, there are neither braking nor driving torques exerted on shaft I40 and the medium 34 may be unwound therefrom without encountering opposition to rotation other than that associated with the friction inherent in the structure. It is thus possible to transfer medium 34 at relatively great velocity without excessive tension thereon.

From Figure 8 it will further be apparent that pin I98 of plate I88 rides on cam I50 at a point of relatively greater radius than the radius upon which it rides in the position of, Figure '7. Thus, cam I50 overcomes the biasing action of spring I92 and cord I24 is tensioned to swing plate 88 in the clockwise direction in opposition to the biasing action of spring 94. As plate 88 is swung about the axis 228 of eccentric 85, the disk 82 is shifted away from brake I and against the enlarged portion 84 of shaft 88, as will be evident from Figure 8. Portion 84 of shaft 68 accordingly drives disk 82 to rotate device 38 in direction to wind medium 34 thereon.

The rotation imparted to device 30 is due to the driving engagement between disk 82 and the enlarged portion84 of shaft 68. The relativ diameters of these disks are chosen so as to achieve the desired linear velocity of medium 34 as it is transferred. In the preferred embodiment of our invention these diameters are chosen 'so that the rewind operation takes about one-tenth as long as the corresponding winding operation, thereby minimizing the time lost during rewind.

When the dial 220 is positioned in the rewind position shown in Figure 8, the rotation of plate I88 about pin I90 is sufiicient to swing idler wheel 204 to the remote position relative to capstan 48 shown in Figures 8 and 10. In this position, idler wheel 204 bears against the extending arm 2I8 of wiper mechanism 2I0, thereby causing the wiper pad to engage medium 34 as it passes over capstan 40. Thus, as medium 34 is drawn over capstan 40 in opposition to the rotation thereof, the medium is pressed against the soft surface of capstan 40 and operates to polish that surface to a uniform radius. This automatically maintains capstan 40 in condition to impart a uniform linear velocity to medium 34 during the forward or wind operation. Certain features of this portion of the mechanism are described and claimed in the copending application of Elmer B. Offutt, Serial No. 747,556, filed May 2, 1947, now Patent No. 2,539,858, dated January 30, 1951, assigned to the same assignee as the present invention.

When plate 88 is moved from the forward position of Figure 9 to the stop position of Figure '7 and moved further to the rewind position of Figure 8, the pin 230 swings about the center of eccentric 86 to engage the extending arm 232 of switch 234. This disconnects wires 236 and 238, Figure 3, to insert a resistance in the circuit of the amplifier so as to reduce the volume of sound to a pleasing level during the rewind operation. Inasmuch as the sound produced during rewind is a reverse intelligence and of no value other than to indicate reversed sition wherein the forward mark thereon is op-- posite reference mark 222, Figure 2, the operative elements of the mechanism are disposed as shown in Figures 9 and 11. This position is necessarily reached from the stop position because dial 220, Figure 2, is held against rotation from the forward position to the rewind position without first going through the stop position or from the rewind position to the forward position without going through the stop position. This is accomplished by extension 224,

Figure 9, of cam I34 which engages the pin I88 of plate I88 to prevent such rotation. This feature not only reduces the wear on the equipment incident to the reversing of direction of travel of medium 34 and minimizes the tendency of the apparatus to tear or break the tape but also assures that erase magnet I32 is in a spaced position relative to medium 34 at all times other than during the recording operation. That is, since arm I28 is automatically swung to the position shown in Figure 2 when the dial 220 is turned to the stop position the action of the operator necessarily swings the erase magnet I32 to a spaced position when the record operation is stopped and the medium is rewound to the original spool. In the absence of this provision of our invention, it would be possible, for example, for an inexperienced operator to leave the erase magnet I32 against medium 34 after making a recording and as a consequence, causing erasure of the medium during the resultant rewind operation.

When the knob 220 is rotated to the forward position of Figure 9, the pin I86 rides on a relatively large radius of cam I84 so that plate I68 is rotated in the counterclockwise direction about pin I10 and the friction surface I14 is swung free of edge I16 of pulley I42. Moreover, pin I64 rides on a point of relatively small radius of cam I50 so that plate I48 is swung by spring I54 in the counterclockwise direction about pin I52. This swings idler I against belt I44 so as to tension that belt and cause a good friction drive between pulley I46, Figure 3, and pulley I42, thereby yieldably driving device 32 in the wind direction.

In the forward position pin I96 of plate I88 rides on a point of small radius of cam I50 so that spring I92 rotates plate I88 in the counterclockwise direction about pin I90 to a relatively great degree. This swings pinch wheel 204 into engagement with capstan 40 as shown in Figure 11 and at the same time releases wire I24 to permit spring 94 to swing plate 88 in the counterclockwise direction about eccentric 86. The engagement between medium 34 and capstan 40 due to the pressing action of pinch wheel 204 under the bias of spring I92 causes a relatively positive driving action between capstan 40 and medium 34 so that linear velocity is imparted to medium 34 in accord with the angular velocity of capstan 40. Inasmuch as capstan 40 is polished to a uniform radius by rewind operations and rotates at a substantially constant angular velocity by reason of the action of flywheel I6 and motor 50,

a uniform linear velocity is imparted to medium to; the lin ar velocity mparte to. medium. 4'. by"

capstan t. Thus. belt M4 slip and maintains. medium 34: am

In the or ar position of Figure plat 8. wipe abou c hter oi. eccen ric '6. o as o cau e- -i-s 8.22 t cheese the irioti n suria e. N1

of brake Him This brake o poses rotation oi. dish 82 and rotation device; at. therebv maintaining: medium. 34 taut as. t s; withdrawn f om: devi e 36.: y the ac i n o cap tan 40.

The rotati n of plat or furth r c ses w per Hit tohear aga n t medium 34 press i a ainst head. 42. T r s l fr m e action. irm L20 of plate as which swings a ains p n Ht to swing; arm M4 in the. ole hwise irec ion about pin H2. as: seen in Figure 11... t er by winging arm, no to. a. correspondin de ree. and. ausin the wiser pad it?) to bear agains the ead 2'- In the orward position of Home. 9 they arm 12.6; is free to sw g so as o cause eras magnet is: to bear a ains medium 3.4 and import. a unitorm ma netization thereto. during, he recordin op ration. This uniform. degr e of magn tizat on.

is hi hly desirable in ord r that the intell g nce orresp nding:- t pr vi us cordings o medium 34 or random no se mpar ed to that mooipi by reason of the. magnetic history of the, ma terials thereof... do come throush to distort the new r cording. This motion f. arm its is made possible by reason o t e foo that late at rotates to the position o Figure. 9,. the lip its is. rotated to a positi n where it does not engage pin Hit of e mifll.

The electrical circuits The electrical circuits of the embodiment of our invention shown and described herein are shown in the schema-tie diagram of Figure 12. In this diagram switches and other components previously described are identified by like reference numerals. Alternating power to the equipment is supplied from terminals 240 and M2 which are connected to a source of alternating voltage. The application of this power is controlled by switch 2M which is attached to volume control rheostat MS to switch the unit off when thevclume control is turned down to zero. In addition, a separate switch 248 is provided selectively to on ergize motor 50 so as to provide independent. control of the operation thereof. The power from the alternating voltage source is applied to trans! former 250 which includes. a plurality of low voltage windings 252 to energize the heater .cir-r. cults of the various electron discharge devices. used in the equipment and a high voltage. winding 254. to provide thev necessary high voltage fiortho. cathode-anode space paths. The terminals of. one winding 252 are connected to the terminals. of the heaters of the various electron dies charge devices. Winding 254 is connected tothe.

full wave rectifier and filter circuit shown genorally at 2.55 so as to produce. at. points 258 and The operation of: the electrica p rt on oi iiivcationv can. best be understo d by cons d rin first. the various. compon nt elements n t e switc 2418- is... rotated to. th -list n p s tion y swihei e arm I26. to. the p iti n show in; Figure Th various component Switches lilo. l lb. etc... are then. positioned as. sh wn n t e s d. lines of. Figure 1.2.. In, this case. passage of medium 34 over head 42 produces a time varying; vol age in w din 8 of head 4 F gure.2,, 1 p hdine; to the v riations. in the gnetizati n. of, medium 34 along its length, This voltage is applied through switch ltib. to the primary winds s; of' ransiormer- 262 which converts t e v a e to a valu suit ble for appl cati n to the c t ol electrode of the first section of electron discharge device 2.64. which forms part of the two stage amplifier shown generally at 26%. By reason oi the amp ifying ac i of amp 26,6, e. time varying voltage induced in the. coil 4.8 appears as: av time varying current flow in resistance 268 so as, to. apply a corresponding time varying voltage tovolurne control potentiometer 266 through the filter network shown generally at Till.

The. filter network 276 acts as an equalizer to: compensate for the constant current. record.-

ol aracteristic oi the recording head and the recording medium. This characteristic causes. approximatelysix decibels per octave. rise. in re.

spcnso up. to a. cut-oi: point and to secure ag ood fidelity or reproduction it is highly desirable to compensate for this uneven characteristic by a, suitable electrical filter or equalizer network. Resistance 2?;2' acts, as atone control to. vary the e i et oi eq l zer-2' e by va yi g the r cu hcr resp se of he quipm n and enablin selective x g e a i n of either hi h frequ ncy or l w frequency c ne ts. t e reproduced signal.

Potenticmeter 2 th acts as a volume control to apply a greater or lesser voltage to the control electrode of the. first; section of electron dischar e device E which fo ms pa t of the two sta amplifier shown generally at 2%. This amplifier J produces two time varying voltages 180 out of phase for.- applioation to the push-pull amplifier shown generally at 278 and which utilizes electron discharge devices 28%} and 28,2. Cathode-anode space current; for devices 251i! and 2&2 flow through the, y "irnary- Winding of transformer 28% so that time ar "he, volt-Jase is produced n the secondary winding 28% thereof which varies accord t e ntelli e ce. T s olt e s applied t h lo d spe ter shown erall at 8 if desi e ttc an xternal rep d ci d e t roueh J k tl- It is thus; evident. that when armiitis rotated to the listen on on wherein switch it! is rotated to the position of the solid lines of Figure 12; the. electrical circuits to amplify the time varying voltage induced in coil :33 in accordance with the variations, in magnetization along the lengthof medi 34 so. as. toproduce, at speaker 28% a time var g signal correspondin to the time o. ai recorded upon medium i i.

The above description of; the electrical circuit applies to. i u tio wh rein knob 2.29 is rotated the forward position and arm iii-t is in the listen position. In this case. switch 234 is. closed and no current flows through resistance 28%.. If knob 22% is; rotated to the rewind position so. that medium 3 is drawn from device it t de ic to at the hi h velo y corr spohd ice. to switch. 2' is op d. by reason he previously described encasement between pil 230 of plate 88 and arm 232 of switch 234 as shown in Figure 8. In this case, resistance 294 is in series connection with the secondary winding 285 of transformer 284 and accordingly reduces the current fiow in speaker 288 to reduce the volume of the reverse recording heard upon rewind to a small pleasant value only sumcient to indicate to the operator that rewinding is in progress.

For the recording operation, arm I26 is shifted to cause erase magnet I32 to bear against medium 34 and to rotate switch I31 to the position shown in the dotted lines of Figure 12. In this condition, dial 220 must be in the forward position because. as previously described, plate 88 prevents shifting of arm I28 to the record position when dial 228 is in any other position. With switch ISI in the position of the dashed lines of Figure 12, jack 296 is connected to the control electrode of the first section of electron discharge device 284 and a suitable signal to be recorded, as for example, a time varying voltage corresponding to music or speech, may be applied through this j ack. In one method of accomplishing this purpose, a microphone (not shown) may be connected to jack 296. The voltage applied to the control electrode of device 264 is amplified by reason of the action of that device in conjunction with the amplifier shown generally at 256 so as to apply to equalizer 210 a time varying voltage corresponding to the intelligence to be recorded. This voltage is applied from equalizer 210 to potentiometer 246 which acts as a volume control to select the level of recording and apply the resultant voltage of the control electrode of the first section of device H4. The resultant out-- put voltages from the amplifier 216 are applied to the two electron discharge devices 288 and 232 comprising amplifier 2'l8 to cause current fiow in the primary winding of transformer 284 varying in accord with the signal to be recorded. This current fiow causes corresponding voltage to be induced in the secondary winding 286 of transformer 284, thereby applying voltage through switch I3Ie and'resistance 298 to the winding 48 of head 42. The resulting current flow causes the magnetic field of head 42 to vary in accord with the time varying voltage applied to the control electrode of device 254 from jack 286. Since the medium 34 is drawn across head 42 at a uniform linear velocity and a constant degree of magnetization is imparted thereto by reason of the action of erase magnet I32, variations in the magnetiziticn in the medium 34 are imparted along its length in accord with the time variations of the signal applied to the control elec-- trode of the first section of device 254 and a recording suitable for later reproduction is produced.

It is the function of the oscillator shown generally at 300 to generate a high frequency voltage for simultaneous application to winding 48 with the voltage corresponding to the signal to be recorded. This oscillator operates at a frequency of approximately 18 kilocycles determined principally by the natural resonant frequency of the inductor 304 in conjunction with the capaci tor 308 and utilizes the conventional Hartley circuit wherein positive feedback is achieved by connecting a tap on inductor 304 to the cathode of device 302 and the opposite ends of inductor 304 to the control electrode and anode of device 302 Winding 3H8 is'in inductive relationship with inducto-r 304 so that an 18 kilocycle voltage is imparted to that winding and applied through switch ISIb to one section of winding 48 of head 42.

In accordance with the well known laws governing magnetic recording, the application of a high frequency voltage to head 42 simultaneously with the time varying signal voltage prevents the nonlinearity of recording otherwise associated with the curvature of the 3-H curve of the magnetic medium 34 near the region of zero flux density. This high frequency bias voltage does not appear during the playback or listen operation because of the filter action inherent in the electrical circuits, together with the inability of the speaker 288 to reproduce such frequencies and the human ear to detect them.

It is the function of neon lamp m to indicate when volume control 246 is properly adjusted for recording. To this end, lamp cm is connected to point 258 through the voltage divider comprising potentiometer 3 I2, resistance 324 and resistance BIG and to the anode of electron discharge device 280 through capacitor 3I8. The junction of lamp 3H) and capacitor 3I8 is connected to ground through resistance 326. When potentiometer 3I2 is properly adjusted, neon lamp 3H] just fires when the combined voltage associated with the time varying voltage appearing at the anode of device 280 and the unidirectional voltage derived from point 258 are of predetermined value corresponding to the optimum level of recording on medium 34. Thus the lamp 3Hl acts as a means of properly adjusting the degree of magnetization imparted to the medium in accord with the signal to be recorded and prevents either undermagnetiz'ation or overmagnetization.

Lamps 249 and 213 are selectively energized from winding 252 by switch ISI to provide an indication of whether the mechanism is recording or reproducing. These lamps are mounted on the front panel 22, Figure 1.

Jack 292 permits insertion of a signal directly to equalizer network 210 during the recording operation so as to permit use of the unit with a relatively high level source of signals. Such a source might, for example, be the phono connection of a conventional radio receiver.

While we have shown a particular embodiment of our invention, it will, of course, be understood that we do not wish to be limited thereto since many modifications, both in the mechanical and electrical structures disclosed and the arrange-- ment of the elements shown, may be made without departing from the spirit and scope thereof. We, of course, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent in the United States is:

1. In a device to vary a condition of a medium in accord with an intelligence, a magnetic transducer head to impart a controlled degree of said condition to an incremental length of said medium in accord with the time variations in said intelligence, a single drive for said intelligence conditioning device operable in one condition'to cause travel of said medium across said head in a predetermined direction and in another condition to impart no travel to said medium, an era-sing device movable independently of said head and operable in a first condition to erase intelligence or noise from said medium before it reaches said head when traveling in said predetermined direction and in a second condition to an operating position against said medium" or shiftable to a set retracted position of rest spaced from said medium, means interconnecting said erase device and said switch so that said erase device assumes said operating position only when said switch is adjusted to cause current flow in said winding, said reversible mechanism including elements to shift said erase device to said set retracted position of rest when said mechanism is stopped and to prevent shifting of said erase device to its operating position when said mechanism is either in the stop or reverse condition, whereby accidental erasure of said medium is prevented.

8. In a magnetic recording and reproducing system, a head having elements shaped to define a path for magnetic flux and a winding disposed to link said path, a lengthy magnetizable medium, means to support said medium against said head so that said medium forms part of said flux path, mechanism selectively operable to sto or to draw said medium across said head in either direction, a control device to control said mechanism having a forward position wherein said medium travels in a first direction, a reverse position wherein said medium travels in the opposite direction, and an intermediate stop position wherein said medium does not travel, means in.- cluding a switch selectively operable to impart current flow to said winding in accord with an intelligence or to reproduce as an intelligence the variations of magnetic flux of said path, pivotal support means, an erase device carried by said pivotal support means and shiftable independently of said head to an operating position against said medium or a set retracted position of rest spaced from said medium, means interconnecting said erase head and said switch so that said erase device assumes said first position only when said switch is adjusted to cause cur rent flow in said winding, said reversible mechanism including elements to shift said erase device to said set retracted position of rest when said control device is shifted from said forward position to said stop position and to prevent shifting of said erase magnet when said control device is in said stop position or the said reverse position, whereby accidental erasure of said medium is prevented.

9. In a. device of the type wherein a magnetizable medium is drawn in a forward direction across a stationary head having a coil and a magnetic flux path to record or reproduce intelli gence, said medium forming part of said flux path, IGVCISlblO drive means to cause said medium to travel across said head, a device urging said medium against said head to assure a uniform relationship therebetween, said device comprising a wiper yieldably supported to urge said medium against said head, and interconnecting elements between said wiper and said drive means to retract said wiper to permit said medium to travel free of said wiper in the reverse direction retracted position wherein said wiper is spaced from said medium or an operating position where 20. said wiper engages said medium to urge it against said head, said last mechanism being engageable with said shiftable elements to retract said wiper when said medium travels in one direction over said head.

11. A magnetic recording and reproducing device including in combination on a pair of medium supporting devices, a medium wound about said support devices to be transferable therebetween by rotation thereof, shiftable elements selectively operable to brake one of said support devices, to rotate said one device in the wind direction, or to release said one device for rotation, shiftable elements selectively operable to brake the other of said support devices or to rotate said other device in the wind direction, a recording and reproducing head disposed to be traversed by said medium as it travels between said support devices, means connected to said head and having a switch operable in one position to cause said means to vary the magnetic field about said head in accord with an intelligence and in another position to cause said means to reproduce a signal varying with time in accord wth the magnetization or" said medium as it travels over said head, an erase head, a support means for said erase head interconnected with said switch so that said erase head bears against said medium in the region between said other medium support device and said head when said switch is in said one position and said erase head is in a retracted position away from said medium when said switch is in said other position, a control device to adjust said shiftable elements, said control device having a first position of operation wherein said other support device is rotated and said one support device is braked, a second position of op eration wherein said one support device is rotated and said other support device is released for rotation, and an intermediate position wherein said other support device is braked, and mechanisms interconnecting said control device with said switch so that when said control device is moved from said first position to said second position, said switch is moved to said other position, and when said control device is in said second position or said intermediate position, said switch is blocked against movement to said one position.

HUGH A. HOWELL.

ELMER B. OFFUT'I.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,142,384 Lifiany June 8, 1915 1,170,216 Blanch Feb. 1, 1916 1,844,224 Klappenacker Feb. 9, 1932 2,086,130 Hichman July 6, 1937 2,089,287 Mailoy Aug. 10, 1937 2,328,539 Greenleaf Sept. 7, 1943 2,351,003 Camras June 13, 1944 2,351,005 Camras June 13, 1944 2,351,007 Camras June 13, 1944 2,418,542 Camras Apr. 8, 1947 2,467,507 Stone Apr. 13, 1949 2,495,125 Nemeth Jan. 17, 1950 2,538,892 Begun Jan. 23, 1951 FOREIGN PATENTS Number Country Date 172,296 Great Britain Feb. 26, 1923 459,035

Great Britain 1- Dec. 31, 1936 

